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SECTION
CHAPTER 10
Principles of Evolution
10.1
EARLY IDEAS ABOUT EVOLUTION
Reinforcement
KEY CONCEPT There were theories of biological and geologic change before
Darwin.
Evolution is the process of biological change by which descendants come to differ
from their ancestors. Charles Darwin was not the first scientist to share his ideas about
evolution and how it occurs.
• Carolus Linnaeus proposed that plant varieties, or species—a group of organisms so
similar to one another that they can reproduce and have fertile offspring—can be
crossed to create new species.
• Georges Buffon proposed that species shared ancestors instead of arising separately,
the common thought of the time.
• Erasmus Darwin, Charles Darwin’s grandfather, noted that more-complex forms of
life seemed to arise from less-complex forms.
• Jean-Baptiste Lamarck recognized that changes in physical characteristics could be
passed on to offspring and were driven by environmental changes over time.
The field of geology also offered insights into evolution. Geologists noted that
fossils—traces of organisms that existed in the past—in deeper layers of rock were quite
different than those found in the upper layers. There were several ideas proposed to
explain how such changes occur.
• The theory of catastrophism states that natural disasters such as floods and volcanic
eruptions have happened often during Earth’s long history. These events shaped
landforms and caused species to become extinct in the process.
•
The principle of gradualism states that changes in landforms result from slow
changes over a long period of time.
•
The theory of uniformitarianism states that the geologic processes that shape Earth
are uniform through time. The theory of uniformitarianism, proposed by geologist
Charles Lyell, combines gradualism with the observation that changes on Earth
have occurred at a constant rate and are ongoing. The concept of uniformitarianism
greatly affected Darwin’s thinking.
1. What are three ideas about evolution that scientists had before Darwin’s ideas were
published?
2. Describe Charles Lyell’s geologic theory, which influenced Darwin.
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Reinforcement
Unit 4 Resource Book
McDougal Littell Biology
Copyright © McDougal Littell/Houghton Mifflin Company.
Although Lamarck had ideas that influenced Darwin’s thinking, his explanation of how
organisms evolve was flawed. He thought, for example, that the long necks of giraffes
evolved as generations of giraffes reached for leaves higher in the trees. This idea, which
was later discredited, is known as the inheritance of acquired characteristics.